Temperature control apparatus



Oct.v v 16, 1945. K. LuToMlRsKl 2,386,903

TEMPERATURE CONTROL APPARATUS Y Filed July 3l, 1941 U5 G cuni/v1' +/4of r lo CURRENT A TTORNEV e Patented Oct. 16,

TEMPERATURE coN'rsoL APPAnA'rU l Karel Lutomirski, Brooklyn, N. Y.,-` assigner -to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application .my s1, 1941, sensi No. 404.869

4` claims (c1. 21a-zo) This invention relates to temperature control apparatus, and more particularly to an arrangement to compensate for relatively wide variations in ambient temperature in'such apparatus.

Heretofore. temperature control arrangements have been utilized to compensate for the etiects of variations in ambient temperature on devicesv embodied lx1-.signaling systems for' the purpose of maintaining a certain overall level of transmission. In this connection, one familiar type of temperature control arrangement has been employed to adjust the gain of individual repeaters embodied in successive sections lof a relatively long transmission line, each of which sections is Y subject to a relatively wide temperature variation during a twenty-four hour period. While 'such temperature compensation is effective to a limited extent, it is not sumciently sensitive to provide.

the degree of temperature controllreuuired to keep in step with repeaters ofixnproved design tending to promote highI emciency and iidelitygin signaling transmission systems. i

Accordingly, this invention contemplates an improved temperature control to nullify substantially the effects of relatively wide variations inA ambient temperature on a device embodied in an electrical or mechanical system.

The main object of the invention is to compensate for the effect of relatively wide variations of ambient temperature on an electrical or mechanical device.

Another object is to maintain a device at asubsubstantially within a-variation of 14F. when j heated to +200 F., and a variation Yof 10.5 F.

allel from a second source of substantially con-v stant electrical current.

The second thermoresponsive elementin response'tc a'variation in ambient temperature extending, for example, between +36 F. and +125 F. serves to control the amount of current supplied to the second heating element'such that the first thermoresponsive element, or interior of the housing, is main-tained, for example, substantially within a variation of 10 F. when heated to +160 F. As aconsequence, theiirst thermoresponsive element is caused to controlI the amount of current supplied to the iirstheating element associated with the device whose temperature is to be controlled such that the tein-A perature of the latter is maintained, for example,

whenheatedto+250n g A feature of the invention is thatA the iirst f thermoresponsive element may 'be provided with stantially constant temperature, when heated to a preassigned temperature, for a certain range of variation in ambient'temperature.

Still another object is to simplify the selection of` individual thermoresponsive elements em' bodied in temperature control apparatus. v

' A fur-ther object is tocompensate for variations in current utilized to energize thermoresponsive,

elements. v

In a specific embodiment, the present invention comprises a` device whose temperature iis to be maintained substantially independent of relatively wide variations in ambient temperature, a. first heating elementI therefor and a iirst thermoresponsiva element, both of which elements are energized in parallel from s. iirst source of substantially constant electrical current. The device and first heating element contained in one envelope. and the iirst thermoresponsive element contained in another envelope are enclosed in a suitable housing. A second heating element for the housing" and a second thermcresponsive element contained Yin a further envelope are supplied in para tubular configuration within `which are positioned the device whose temperature is to be controlled andthe first heating element therefor so as to eliminate the need for 'the housing. Another feature is that the device whose temperature is to be controlled may be maintained substantially independent ci variations in the am'ount of current supplied thereto by the i'irst'source of electrical power. A further vfeature obviates the selection of individual thermoresponsive elements on a basis of Yexact precision as heretofore re quired in single-stage temperature control apparatus for the reason that in the` present inven-l tion precise sensitivity may be obtained by means of two or more stages of temperature control. An additional feature is that the nrst thermoresponsive element may comprise a resistance element having either a positive or negative temperature coemcient of resistance.` A further feature provides finer temperature' control by indirectly heating the individual thermoresponsive elements to accomplishl in effect a'feedback action between the individual heating elements and thermore-l sponsive elements. The invention will be readily understood from the following description taken together with the accompanying drawing in which:

' Fig. 1 is a schematic circuit illustrating a specific embodiment of the invention; v Fig. 2 is a schematic circuit showing amodiiication of Fig. l', ,l A

Fig. 3 is a schematic circuit sbcwins another embodiment of the invention;

Y `'2,231,558 granted February 11, 1941,.

Y Fig. 4 is a schematic circuit representing -a modiication of Fig. 3;

Fig. 5 is a schematic circuit illustrating another embodiment of the invention;

Fig. 6 is a schematic circuit which is a modification of both Figs. 3 and I5; Figs. 7, 8 and 9 are schematic circuits showing modiiicationsof Figs. 3 and 6 in the respect that certain thermoresponsive heated; and y Fig. 10 is a schematic circuit showing another embodiment of the invention.

Referring to Fig. 1, the temperature of electrical apparatus I is to be maintained substantially independent of relatively wide variations in ambient temperature. In other words, the temperature of the apparatus I0, when heated to a preassigned amount, is to be maintained substantially constant regardless of a relatively wide variation in ambient temperature.

The apparatus Ill4 may comprise various material utilized for particular purposes in electrical or mechanical systems. For example, the apparatus I0 may comprise a thermoresponsive element for controlling the gain of a repeater as illustrated in the patent of J. H. Bollman, No.

elements are indirectly -nection the apparatus I0 is a thermistor, or resistance element, having a high negative tem perature coeicient of resistance of which silver sulphide, uranium oxide; and boron are wellknown examples, and is enclosed in an envelope 8. The apparatus I0 may also comprise a crystal of a crystal-filter, a tuning fork in an oscillation system, or other apparatus whose temperature is to be controlled. r

Disposed in the envelope 8 in close proximity of the apparatus I0 is a heating element II which is connected to a source I2 of substantially constant current. A thermistor I3 enclosed in an envelope 2| and having a high negative temperature coelcient of resistance is also connected to the current source I2 in parallel with the heating element II. A, suitable housing 9 encloses the respective envelopes 8 and 2i embodying the apparatus I3, heating element II and thermistor I3. Positioned in close proximity of the housing 9 is a heating element I4 which is applied to a source I of substantially constant current. A vthermistor I8 enclosed in an envelope I9 and having a high negative temperature coemcient of resistance is also'connected to the current source I5 in parallel with the heating element I.

In the operation oi Fig. 1, variations in the eilective resistance of the thermistor I8 in response to variations in ambient temperature extending, for example, over a range between +36 F. and +125 F. serve to control the amount of current supplied to the heating element I4 from the source I5 such that the interior of the housing 9 including the thermistor I3 is substantially maintained, for example, within a variation of .LI-10 F. when heated to +160 F. Such temperature control of the thermistorI causes variations in the eiective resistance thereof to control the amount of current supplied to the heating element II from the source -I2 such that the temperature of apparatus I0 is substantially maintained within a variation of 24.0 F. when heated to +200 F. and $0.5" F. when heated to Thus, the heating Velement II and associated In this conv mistor I3 of the latter is provided with a tubllar'` coniigu'ration within which are disposed the apparatus I0 and heating element II therefor, and about the periphery of which is applied the heating element Ill.' Links I'I and I8 serve to connect the tubular thermistor I3 to the source I2 in the manner mentioned regarding Fig. l. The temperature control specied hereinbei'ore for Fig. 1 also obtains for Fig. 2. Thus, the tubular thermistor I3 oi' Fig. 2-may effectively replace/ the housing 9 oi' Fig. 1. v

Fig. 3 is identical with Fig. 1 except a thermistor 20 is applied in shunt oi the heating element II and is also heated thereby. Hence, when the amount of current supplied by the source I2 increases, the resistance of the thermistor 20 decreases, thereby eilg'ectively decreasing the amount of current owing in the heating element II and when the amount of current supplied by the source I2 decreases, the resistance of the thermistor 20 increases thereby electively increasing the amount of current flowing in the heating element II. This is, in eiect, a feedback action between the heating element II andy thermistor 20.- Thus, an amount of current is supplied to the heating element II such that the temperature of the'apparatus I0 is rendered substantially g indepedet of variations in the 4amount of current supplied by the source I2.

l thetubular thermistor I3 of Fig. 4 may replace the apparatus l0, when heated toa preassigned the housing 9 of Figs. 1 and 3.

Fig. 5 is the same as Fig. 1 except a pair olf resistorsv 25, 25 having positive temperature coeili cient of resistance is substituted for the thermistors I3 and I6, and are individually connected in series with the heating elements II and I4. Obviously, the same substitution could be readily made in Fig. 3.

Fig. 6 is a combination of Figs. 3 and 5 and includes both the thermoresponsive elements 20 and 25.

Fig. I is a'modication of Figs. 3 and 6 in the use of the thermistor 20 of .both latter figures. Referring to Fig. 7, the temperature, or eiective resistance, of thermistor 29 mounted in envelope 28 and having a high temperature coefficient oi resistance is controlled by current owing therethrough, a certain range of variation of ambient temperature, and heat due to heating element 30 which is also contained in the envelope 28 and which is connected in series with the heating element 3'I utilized to heat the apparatus I0 mounted perature is to be controlled. This arrangement enables a control oi' the amount of current sup-- plied by a source I2 oisubstantially constant currentfto maintain,- ior example, the temperature of the apparatus i at approximately +140' FQ :3' for range of variation voi ambient tempera- .sir r". tofs-140 r'. 1 a

The thermistor 2s, dueto its'change of resistturc, for example, extending approximately'irom ance, and the heating lelement l0 constitute in eifect a feedback action relative to the current suppliedby the source 32. Thus, the arrangement o fFig. 'l provides a sensitive control of the temperature of the apparatus Ill with respect to both variations in the amount of current supplied by the source 32 and variations in ambient temperature.

Fig. 8, is the same as Fig. 'l except the heating element Il is connected in parallel with the heating element 3l.

l accesos, in an eaveioperi with the um; and whose temsuch that the temperature or the apparatus lo is maintained at the above-mentioned tempera- `that the smaller enclosure is positioned within the next larger enclosure, said apparatus being positioned within the innermost enclosure, a heating element positioned within the innermost enclosure in heat-transfer relation to said apparatus, a source oi constant current for energizing said heating element, and means including a resistor havinga temperature coeillcient of resist- Y ance connected to both said source and said heating element and continuously responsive to variations ot the' temperature external to the innerf most enclosure to change its effective resistance Fig. 9 shows two stages ci' the arrangement of Fig. 'I to obtain closer temperature regulation of lthe apparatus I0. Referring to Fig. 9 a housing Il encloses the apparatus lil, heating element 3i thereionthermistor '28 and heating element 3i) therefor. A heating ,element Il heating the interior oi-thefhousing 3l is energized from a source $5 of4 substantially constant current. A thermistor 36 havinga high temperature eoemcientof resistance is applied in shunt of both the heating elements ll and 31 in series. A-heating element for continuously controlling the eiiective amount of current energizing said heating element such 'that the temperature Awithin the innermost enclosure, and Ythereby the temperature of said ap- I1 Afor the thermistor 38, is mounted in envelope together with the latter. According to the arrangement of Fig. 9, the' temperature of the apparatus i0 is maintained, for example, approximate- 33. for example, approximately at +140 F. ';10, and the thermistor 36 is subject, for example, to an ambient temperature variation of F. to p 14o"A F.

It is understood that Fig. 9 may include at least two stages ci' the arrangement shown in Fig. 8,

ora combination oiboth Figs. 7 and 8;. and further that a more sensitive control ci the temperature of the apparatus It may be obtained by utilizing .more than two stages'. of the various figures .discussed above.

Fig. 10 shows an arrangement i'or maintaining the apparatus i0 at a temperature which is relatively close to the maximum ambient temperature. Heretofore, it has been found diilicult to maintain the apparatus i0 at an approximate temperature o! +160 F. 13, for example, when the temperature of thermistorl having a high temperature coefilcient of resistance is subject to a variation in ambient temperature extending, for example,.irom +36 F. tti-+125? F. Although 'a plurality oi stages oil temperature control as hereinbefore discussed may suiilce to provide the speciiied temperature control,it may happenthat such stages may be objectionable in certain circuit designs. Rei'erring to Fig. l0, the speciiled temperature control may be expeditiously con- .'trolled by applying to thermistor 4U and heating to the heating element 4I' from the source I2 ly at i- 160 F. 10.5,- the interior oi the housing paratus, is maintained substantially constant.- 2. vIn combination. in. an arrangement for continuouslyjregulating temperature, including two enclosures one of which is positioned within the other, and apparatus whose temperature is to be regulated and which is positioned in said one enclosure, means for continuously maintaining said apparatus substantially at a preselected temperature, comprising one heating means positioned in said one enclosure in heat-transfer relation to said apparatus, other heating means positioned exteriorly of said other enclosure in heat-transfer relation thereto, current supply means for energizing each of said heating means, and thermosensitive elements having individual temperature coemcients of resistance and coni/iectedv in circuit 11th said respective heating means and said current supply means for continuously controlling the effective amount of current supplied to said respective heating Vmeans such that one thermosensitive element positioned exteriorlyof said other enclosure varies its eiective resistance in response to a certain range oi ambient temperature for substantially maintaining the temperature in said other enclosure within a preselected range of variationwith reference to a predetermined temperature and such that the other thermosensitive element positioned interio'rly oi said other enclosure varies its eective resistance in response to the preselected range of i temperature variation in said other enclosure for maintaining the temperature oi lsaid apparatus substantially at said preselected temperature.'

3. YThe combination according to claim 2 which includes a further thermosensitive element having a temperature coemcient o! resistance and positioned in said one enclosure in heat-transfer relation to said one'heating means and connected -in parallel therewith to change its effective resist.-

ance in response to variations in the amount of current supplied by saidcurrent supply means for further controlling the eiective amount of.

current supplied to said one heating means thereby to compensate said preselected temperature of said apparatus for the tendency of said current supply means to vary the amount oi' current supplied thereby.

4. In a system for maintaining the temperatureof a device substantially independent 'of atmosphere temperature fluctuations including enclosures one inside another with said device inside the innermost enclosure, one heating element for the outer enclosure and another heating elen ment for the innermost enclosure, a source of steady heating current supplying each of said heating elements, and resistors having a high temperature coeilicient of resistance. veach said resistor exposed to the temperature nuctuations in its immediate surrounding space. said resistors being connectedin circuit with seid heating cur rent supply source and respectively controlling the amount ot heating current supplied to the 'respective heating elements for the respective enclosures as a function ot thetemperature variotion ot the respective resistors, one of said resistors being outside the outer enclosure and another being inside thel outer enclosure, said heating element for said inner most enclosure being inside thereof with said device and connected to said last resistor, and said heating element for said outer enclosure being outside thereof and con- 10 nected to scid one resistor.

mmm Lu'ro.y 

